[CentOS] 2.6.18-92.1.6.el5xen -- 8GB missing?

Sun Jul 13 00:11:28 UTC 2008
JJB <jack at internetguy.net>

Hello,

Last night I upgraded a server to CentOS 5.2.  The server has 16GB of
RAM.  Now that it's running 2.6.18-92.1.6.el5xen only 8GB is reported to
exist.

# cat /proc/meminfo
MemTotal:      8818688 kB
MemFree:       3730124 kB
Buffers:        202004 kB
Cached:        4086788 kB
SwapCached:          0 kB
Active:        1551480 kB
Inactive:      2958196 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:      8818688 kB
LowFree:       3730124 kB
SwapTotal:     8388600 kB
SwapFree:      8388600 kB
Dirty:            7348 kB
Writeback:           0 kB
AnonPages:      220788 kB
Mapped:          46948 kB
Slab:           137404 kB
PageTables:      29012 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:  12797944 kB
Committed_AS:   756072 kB
VmallocTotal: 34359738367 kB
VmallocUsed:      5004 kB
VmallocChunk: 34359733235 kB

However, dmesg appears to report something else:

# dmesg | grep Memory
Memory: 15506152k/15899468k available (2417k kernel code, 384480k
reserved, 1350k data, 176k init)

I looked in the messages file for complaints and didn't see anything
that strikes me as unusual.

How much memory is available?  Is this a known issue?